I have two forms on a page (one is being grabbed by AJAX). I need them both to be posted, so I serialize the second one and send it in a post using jQuery before submitting
You might try submitting "first_form" in a callback from the post of "second_form". I believe that the submit of "first_form" is unloading the page which causes the second post to be aborted. Doing the post of "first_form" in the callback from "second_form" will ensure that the initial post is complete before the second post begins.
$("#submit").livequery('click', function() {
var form = $("#second_form");
var action = form.attr("action");
var serialized_form = form.serialize();
$.post(action, serialized_form, submit_first);
});
function submit_first(val) {
$("#first_form").submit();
}